Hot Corrosion of Cobalt-Base Alloys
Final technical rept. 1 Jun 1972-31 May 1975
PRATT AND WHITNEY AIRCRAFT GROUP EAST HARTFORD CT
Pagination or Media Count:
The sodium sulfate-induced hot corrosion of cobalt and a number of binary, ternary and quaternary cobalt-based alloys containing aluminum, chromium, tungsten, molybdenum, tantalum, titanium and yttrium has been studied at 1000-degrees Celsius in 1 atm of oxygen or air. The studies consisted of both laboratory experiments and testing with a dynamic burner rig. The results obtained from these studies were compared to those available for equivalent nickel-base systems. Those obtained from laboratory tests were in satisfactory agreement with those from dynamic burner rigs except that the loss of chromium from the alloys was more pronounced in the high velocity rig tests. It was determined that sodium sulfate deposits caused increased oxidation of all of the alloys studied. Mechanisms for the hot corrosion of these alloys have been developed. A substantial difference between the hot corrosion resistance of cobalt- and nickel-base alloys has been observed only for alloys containing chromium and aluminum with no refractory elements. Chromium and yttrium produced beneficial effects on the hot corrosion of alloys aluminum also produced beneficial effects except at low concentrations of aluminum. Molybdenum and tungsten usually produced deleterious effects on the hot corrosion of alloys whereas tantalum and titanium were apparently innocuous.
- Properties of Metals and Alloys